Engine Noise in the V8 Automatic at 1400 rpms - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

jimfin · 08-27-2009, 03:45 PM

There is something that I noticed and are wondering if anyone else with the V8 Automatic hears the same thing. When I'm driving in the streets and i hit the gas and get the car up to 2000 rpm's it sounds normal. If I have to slow down and the rpm's drop down to 1200-1400 rpm's there is a sound that comes from the engine almost as though its down shifting, but its very pronounced. I don't lose any power, but it doesn't sound right to me. I had my exhaust upgraded (GM Performance) and an air box installed and now the noise sounds more "raspy" for lack of a better word. My machanic noticed this, but had no explanation. He really doesn't know enough about the car to tell me if this is normal. Is it possible the L99 engine steps down cyclinders (goes from 8 to 6) at lower speeds and thats what I hear. Any help will be appreciated. Thanks

Gentry78 · 08-27-2009, 04:07 PM

Quote:

Originally Posted by jimfin

There is something that I noticed and are wondering if anyone else with the V8 Automatic hears the same thing. When I'm driving in the streets and i hit the gas and get the car up to 2000 rpm's it sounds normal. If I have to slow down and the rpm's drop down to 1200-1400 rpm's there is a sound that comes from the engine almost as though its down shifting, but its very pronounced. I don't lose any power, but it doesn't sound right to me. I had my exhaust upgraded (GM Performance) and an air box installed and now the noise sounds more "raspy" for lack of a better word. My machanic noticed this, but had no explanation. He really doesn't know enough about the car to tell me if this is normal. Is it possible the L99 engine steps down cyclinders (goes from 8 to 6) at lower speeds and thats what I hear. Any help will be appreciated. Thanks

the L99 only goes V8 to V4 and back never does it go to 6, just to clear that up for ya

does it only do it when off the gas or does it do it during cruising as well

Sloppy Joe · 08-27-2009, 04:17 PM

It's the AFM kicking in and out that your hearing. A bit annoying, but its completely Normal for the L99. Gentry is right its 8 to 4 , there is no 6 cylinder mode.

BlemsBumble · 08-27-2009, 11:26 PM

Get used to it.

JSOC_MQ1 · 08-27-2009, 11:30 PM

That noise is why the stock exhaust has the "huge" resonators on it. You will hear the same thing if you are crusing down the highway and start to go down a hill.

Kyle.Gilmour · 08-28-2009, 10:31 AM

It sounds like the guys here may have pinpointed the problem for you.

But last week I had my AC compressor replaced... it had a bad bearing.... from the day I picked it up it was making a whining noise at certain RPMs close to what you mentioned.

Just in case my explanation sounded familiar. I have an LS3 though.

DDustiNN · 08-28-2009, 10:44 AM

Quote:

Originally Posted by Kyle.Gilmour

It sounds like the guys here may have pinpointed the problem for you.

But last week I had my AC compressor replaced... it had a bad bearing.... from the day I picked it up it was making a whining noise at certain RPMs close to what you mentioned.

Just in case my explanation sounded familiar. I have an LS3 though.

What did it sound like? I noticed a noise from behind my dash, toward the center, when I'd rev somewhere betweek 2-3k RPMs. It's hard to explain the noise, but it almost sound like a "tinny" noise or something... Gah, I really don't know how else to describe it. I'll see if it's still there when I get my car back. If it is, I guess I'll have the dealer check it out.

BrianGriffin78 · 08-28-2009, 10:50 AM

That is the cylinders shutting down from 8 to 4, to give you the better gas mileage. If you drive in M mode, aka Sports mode you should not hear that.

DDustiNN · 08-28-2009, 11:17 AM

Quote:

Originally Posted by BrianGriffin78

That is the cylinders shutting down from 8 to 4, to give you the better gas mileage. If you drive in M mode, aka Sports mode you should not hear that.

Does Sport Mode eliminate AFM? I haven't heard of that before... That would be interesting...

Kyle.Gilmour · 08-28-2009, 07:41 PM

Quote:

Originally Posted by DDustiNN

What did it sound like? I noticed a noise from behind my dash, toward the center, when I'd rev somewhere betweek 2-3k RPMs. It's hard to explain the noise, but it almost sound like a "tinny" noise or something... Gah, I really don't know how else to describe it. I'll see if it's still there when I get my car back. If it is, I guess I'll have the dealer check it out.

If the AC is off, it wont make the noise. If you are wondering if it is the same thing, shut the AC off and see if it stops.

BlemsBumble · 08-28-2009, 11:52 PM

Quote:

Originally Posted by DDustiNN

Does Sport Mode eliminate AFM? I haven't heard of that before... That would be interesting...

Not a chance.

ravensjeff · 08-29-2009, 12:28 AM

I thought I read that the v8-v4 shift happens near the 1800 rpm spot.

29er · 08-29-2009, 12:39 AM

turn up the radio higher.. just a joke!.. have it road tested at your dealer ...

jimfin · 08-29-2009, 01:30 AM

Quote:

Originally Posted by Gentry78

the L99 only goes V8 to V4 and back never does it go to 6, just to clear that up for ya

does it only do it when off the gas or does it do it during cruising as well

Off the gas

08-27-2009, 03:45 PM	#1
jimfin Drives: 2SS, Yellow/RS, Volvo XC90 Join Date: Jul 2009 Location: Long Island Posts: 93	Engine Noise in the V8 Automatic at 1400 rpms There is something that I noticed and are wondering if anyone else with the V8 Automatic hears the same thing. When I'm driving in the streets and i hit the gas and get the car up to 2000 rpm's it sounds normal. If I have to slow down and the rpm's drop down to 1200-1400 rpm's there is a sound that comes from the engine almost as though its down shifting, but its very pronounced. I don't lose any power, but it doesn't sound right to me. I had my exhaust upgraded (GM Performance) and an air box installed and now the noise sounds more "raspy" for lack of a better word. My machanic noticed this, but had no explanation. He really doesn't know enough about the car to tell me if this is normal. Is it possible the L99 engine steps down cyclinders (goes from 8 to 6) at lower speeds and thats what I hear. Any help will be appreciated. Thanks

08-27-2009, 04:17 PM	#3
Sloppy Joe Drives: 2SS RJT Join Date: Mar 2009 Location: Mexico, Missouri Posts: 135	It's the AFM kicking in and out that your hearing. A bit annoying, but its completely Normal for the L99. Gentry is right its 8 to 4 , there is no 6 cylinder mode. __________________ 2SS, RJT, Gray interior, 6 Speed Trans /w TAPshift, silver stripes and polished wheels

08-27-2009, 11:26 PM	#4
BlemsBumble Drives: '13 ZL1 #662; '10 SS; '99 SS Join Date: May 2009 Location: Clovis CA Posts: 457	Get used to it. __________________

08-28-2009, 10:31 AM	#6
Kyle.Gilmour Charter Circle Member Drives: 427 LSX- with TWINS Join Date: Jan 2007 Location: Back in Michigan!! Do miss ATX and my Tejas friends Posts: 2,745 View My Garage	It sounds like the guys here may have pinpointed the problem for you. But last week I had my AC compressor replaced... it had a bad bearing.... from the day I picked it up it was making a whining noise at certain RPMs close to what you mentioned. Just in case my explanation sounded familiar. I have an LS3 though. __________________

08-28-2009, 10:50 AM	#8
BrianGriffin78 Drives: 2009 GMC Yukon Join Date: May 2009 Location: New York Posts: 920	That is the cylinders shutting down from 8 to 4, to give you the better gas mileage. If you drive in M mode, aka Sports mode you should not hear that. __________________

08-27-2009, 11:30 PM	#5
JSOC_MQ1 Drives: 2010 IBM 2SS Join Date: Jan 2009 Location: Missouri Posts: 115	That noise is why the stock exhaust has the "huge" resonators on it. You will hear the same thing if you are crusing down the highway and start to go down a hill.

08-29-2009, 12:28 AM	#12
ravensjeff 100% Chevy & Harley Man Drives: 2010 2SS: Blown LSX 376-B15 Join Date: Feb 2009 Location: Eldersburg,MD Posts: 2,211 View My Garage	I thought I read that the v8-v4 shift happens near the 1800 rpm spot. __________________ LSX 376-B15, TVS2300 SC, Harland Sharp Rockers w/ Trunion Bearings, ATI Balancer/keyed, AR LT Headers/Borla Catback Exhaust, DSS 1400 HP Axles, DSS aluminum driveshaft, 3.70, Hotchkis Springs/Sway bars, Forgeline SO3P Aluminum Wheels (20x9.5 F/20x11 R)w/ Hidden Titanium Hardware, Nitto NT05 Tires (27540ZR20 F/31535ZR20 R), Billet LPE brake/gas pedals, Escort 9500ci Radar Detector Laser Jammer, Roto Fab CAI with Ice Silver box, Carbon fiber tube/MAF Housing Assy, LPE Aluminum coil covers, SS9 Sleeper Fiber Glass Hood (ACS), Carbotech 1521 ceramic brake pads, Elite catch can.

08-29-2009, 12:39 AM	#13
29er Drives: 14 1LE Garage King Join Date: Jan 2009 Location: MTL Posts: 1,519 View My Garage	turn up the radio higher.. just a joke!.. have it road tested at your dealer ...

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